How to Treat Fusarium & Verticillium Wilt

Fusarium and Verticillium wilts attack tomatoes and other vegetables and ornamental plants in the garden. Fungi found in the soil invade the root systems of susceptible species and cause yellow leaves, wilting and leaf drop. The diseases are frequently discussed together because they produce similar symptoms in plants. Unfortunately, you cannot treat either disease in your plants once infected. Particularly with Verticillium wilt, your plants may survive, although productivity becomes severely limited. You can undertake preventative measures, however, to keep the disease from plaguing your garden plants in subsequent years.

Knife

Clear polyethylene tarp

Examine the plant for wilted, yellow foliage. Although, for both diseases, symptoms typically begin at the base of the plant and affect the older foliage first, Fusarium wilt often produces symptoms on only one side of the plant. In some cases, Fusarium symptoms appear on only one side of the leaf. Verticillium symptoms, on the other hand, occur on both sides of the plant.

Make a vertical slit into the stem near the base of the plant. Both wilts affect the vascular tissue of the plant, causing a layer of brown discoloration to develop just below the surface of the stem. Fusarium tends to extend further up the plant's stem than Verticillium.

Contact a plant diagnostic laboratory -- often available through your local extension office -- and collect samples as instructed to distinguish between the diseases if you can't diagnose the problem using symptoms alone. A definitive diagnosis requires lab analysis.

Remove infected plants promptly from the garden and destroy them. Do not compost them because this will spread the pathogens back into the soil.

Rotate crops. Avoid planting susceptible plants on soil known to be infected by one or both diseases for at least four to six years.

Plant resistant varieties. Plants labeled F or V have a genetic resistance to Fusarium and Verticillium, respectively.

Solarize the soil to kill existing pathogens. Cover the infected soil with a clear polyethylene tarp during the hottest and longest days of summer. You will need to leave the tarp in place for four to eight weeks, depending on the temperatures common in your area, in order to kill pathogens. Solarization destroys Fusarium and Verticillium spores up to 8 inches deep in the soil.

Provide adequate water and fertilizer for the plants, and keep the garden weed-free. Healthy, non-stressed plants better resist diseases, and many common garden weeds can act as alternate hosts for the diseases, allowing them to persist longer in the soil.

Verticillium wilt also affects some tree species. It is not always fatal, and you should wait to observe the progress of the disease before removing the tree. Keep the trees well watered to improve their chances of survival and remove infected branches to reduce the likelihood of secondary infections that further weaken the tree. If you must remove infected trees, do not use the woodchips as mulch unless they are properly heated by a hot compost or solarization process.